In recent years, use of digital equipment such as cellular phones, digital cameras, personal computers and the like has been spread significantly. Thus, technical development in data transmission among such equipment by using infrared radiations or visible lights has been pursued actively.
For example, Japanese Laid-Open Publication No. 10-56427 discloses a technique to transfer data from a personal computer or the like to a printer by using infrared radiation transmission. Japanese Laid-Open Publication No. 9-36805 discloses a system for performing data transmission between a public telephone and a cellular phone by using infrared radiations.
As a data transmission utilizing visible lights, Japanese National Phase PCT Laid-Open Publication No. 2002-527917 discloses a system for data communication among personal computers using visible lights emitted from LED dot matrix displays. Further, Japanese Laid-Open Publication No. 2000-344103 discloses a technique for optical transmission of various types of information such as vehicle velocity and the like to vehicles by using blue, read, and green visible light of a traffic signal.
Recently, more and more slim-type large-screen image display devices such as liquid crystal televisions, rear-projection type television, and organic EL displays have been replacing conventional CRT televisions. With such image display devices, additional information such as teletext broadcasting, program information and the like can be easily obtained.